Prehistory

Giants of the Past
Dinosaurs died out millions of years ago, but these prehistoric creatures still fascinate us today. No wonder, for they were masters of the land some 75 times longer than humans have been living on the earth. Dinosaur discovery started in the 1820s, when scientists began to realize that the huge fossil bones they found in ancient rocks belonged to prehistoric creatures unlike anything now alive. Bit by bit, anatomists pieced the bones out the animals' shapes and sizes, as well as how they stood, walked fed and fought. Because so much was guesswork, they made many mistakes. Skulls were sometimes placed at the tip of a tail and a spiked thumb was once mistaken for a horn! Since those first discoveries, scientists who probe the past have learned a great deal more about the dinosaurs. We now long-legged, hunting reptiles and not much bigger than a rabbit. True dinosaurs appeared about 230 million years ago. Over time, they spread to all the continents, which wee then joined together to form one huge supercontinent. Different kinds of dinosaurs developed. From the first two-legged meat-eaters came many more. The smallest grew no bigger than a cat; the largest weighed as much as an elephant. Such predators were the biggest hunting animals that ever lived on land.

These eight dinosaurs include four plant-eaters and four flesh-eaters. Brachiosaurus browsed among the treetops while Triceratops, Edmontosaurus and Stegosaurus cropped leaves nearer the ground with their horny beaks. Compsognathus and Ornitholestes were small hunting dinosaurs that chased lizards through the undergrowth. Deinonychus may have killed medium-sized plant-eating dinosaurs by slashing at them with its claws. Tyrannosaurus probably charged big dinosaurs head first, taking great chunks of flesh out of their sides with its huge jaws.


 * Triceratops horridus (Shaggy three-horned face)
 * Ornitholestes hermanni (Herman's bird robber)
 * Brachiosaurus altithorax (High chest arm lizard)
 * Edmontosaurus regalis (Royal Edmonton lizard)
 * Compsognathus longipes (Long-footed pretty jaws)
 * Deinonychus antirrhopus (Counterbalancing terrible claw)
 * Stegosaurus armatus (Armoured plate lizard)
 * Tyrannosaurus rex (Tyrant lizard king)

These monsters preyed on plant-eating dinosaurs. They too branched out into many kinds. Small, two-legged plant-eaters gave rise to much larger animals. Most of these walked on all fours. Plant-eaters built like monstrous giraffes included the longest and heaviest land animals of all time. Between them. hunting an plant-eating dinosaurs filled the places taken today by mammals such as lions and cheetahs, deer, antelopes, giraffes and elephants. By 1990, scientists had named hundreds of different kinds of dinosaur. Many of these have been named since 1970 and new discoveries are made every year. As each new discovery is made, scientists change their ideas about what the dinosaurs were like. People used to think of dinosaurs as cold-blooded animals. These need the Sun's heat to make them warm enough to move around. Today, many scientists believe that dinosaurs' bodies were always warm, much as mammals' bodies are. People once thought of dinosaurs as slow plodders. Scientists now believe that some could run as fast as a horse. Because most dinosaurs had tiny brains, people used to think they were stupid. Now we know that many were quite crafty creatures and that some led fairly complex lives. Then, about 65 million years ago, the dinosaurs died out.. Their sudden disappearance is just one of the many mysteries that scientists still puzzle over today.

In the pages that follow, we shall trace the story of the dinosaurs. You will find some words are in bold type. This means that they are explained further in the Glossary.

The Fossil Hunters
Most of what we know about the dinosaurs comes from bones and tacks that have been preserved as fossils in rocks. The Ancient Greeks noticed fossil animals more than 2400 years ago. But no one knew for sure how fossils were formed By about 400 years ago, scientifically mined people realized that sea. Somehow the shells had become stuck in rocks on land, even high up on mountains. But how? One popular explanation was that a great flood had once drowned the world then left the shells high and dry. How fossils were really formed remained a mystery until about 200 years ago.

How Fossils Really Formed
We now know that most fossil dinosaurs are the remains of corpses that fell in rivers, lakes or seas and settled on the mud or sand below. The dead dinosaurs' soft parts soon rotted mud or sand. This save then from decay. In time, thick layers of mud and or sand built up, squashing the layers beneath. These slowly hardened into limestone, sandstone and other minerals down through the rocks filled tiny holes in the buried dinosaur bones. The minerals strengthened the bones against the pressure of the rocks above and the bones were preserved as fossils. Dinosaur teeth, however, were so hard that many have survived almost unchanged. Sometimes, a bone dissolved away and a left bone-shaped hole. This is called a mould. If minerals filled the hole, they formed fossil called a cast. Moulds and cast are very rare, however.

After millions of years, earthquakes thrust some fossil bearing rocks above the sea. Rain, wind and frost gnawed away parts of the rocks and the fossil dinosaurs were left exposed. Of the millions of dinosaurs that once walked the Earth, however, very few ever became fossils. Even fewer show up on the surface and be found.

This dead dinosaur (1) is a fossil in the making. Its body is washed away by the river and settles on the rive bed. There its soft pants rot away, leaving only the hand skeleton.

This is covered by layers of mud and, in time, minerals replace the bone (2). As more layers build up, the pressure gradually turns the bones into rock. They have become fossils (3).

Much later, earth movements push the fossil up to the surface where it is uncovered by the action of wind and rain (4).

The Hunt Begins
As long ago as 1677, Dr. Robert Plot, an Oxford professor, described a dinosaur thigh bone that he had found. Dr. Plot thought the huge bone came from a giant man. It wasn't until the 1820s that people realized that these bones belonged to huge animals that no longer existed. The first dinosaur discoveries were made in England. In 1821, Professor William Buckland of Oxford University described strange, ancient bones that had been dug up near Oxford. Among them was a large jawbone with teeth like knives. Buckland called its prehistoric owner Megalosaurus ("giant reptile"). Megalosaurus was the first dinosaur to get a proper, scientific name.

At abut the same time, Mary Mantell, a doctor's wife noticed some fossil teeth lying in a pile of roadmenders' stones. She collected them for her husband, who was a keen fossil hunter. Dr. Mantell realized that the teeth must have belonged to an unknown, giant prehistoric creature. In 1825, he named is Iguanodon ("iguana tooth"), because its teeth reminded him of an iguana's lizard's teeth. Over the next few years, workmen unearthed more fossil teeth and bones in southern England. The leading anatomist of the time, Sir Richard Owen, concluded that they belonged to a group of mighty, prehistoric reptiles. In 1841, he named the group dinosaurs, which comes from two Greek words that means "fearful reptiles".


 * In 1677, Dr. Robert Plot was the first person to describe a dinosaur bone.
 * In 1822, Mary Mantell found some fossil teeth in a pile of stones by the roadside. They belonged to an Iguanodon.
 * Dr. Gideon Mantell described the plant eater Iguanodon, the second dinosaur to get a scientific name.
 * A nest of the fossil eggs of Protoceratops. The eggs are 20 centimetres long and were laid in a hollow scooped out of the sand. The female Protoceratops probably covered them with sand and let them hatch in the Sun's heat.
 * Workers in the early part of this century had to use a pulley and muscle power to raise the heavy fossil thigh bone of a Diplodocus.

Monsters from North America
More dinosaur bones were discovered in England and other European countries throughout the rest of the 1800s, but the most exciting finds began to come from North America. In 1877, two school teachers independently found huge huge fossil bones in Colorado, in the western United States. One showed his finds to Othniel Marsh, a wealthy American palaeontologist. The other showed what he had found to Marsh's rival, Edward Cope. Marsh and Cope began to race to see ho could dig up the most, and the largest, dinosaur fossils. Armed against attacks by Indians, their teams of fossil hunters around the West. Marsh really won the race, discovering 25 "brand-new" kinds of dinosaur, compared to only 13 for Cope. Their discoveries laid the groundhawk for what we know today about the Age of Dinosaurs. In the 1880s, more dinosaur bones were found in the Canadian province of Alberta, and since 1900, fossil hunts have uncovered dinosaur fossils on every continent of the globe.

Hunting Dinosaurs Today
Today's fossil hunters may have tools the fossil hunters of the 1800s would have envied, but people still discover fossils in much the same way. First, they must find rocks which were formed in the time of dinosaurs, some 65 to 230 million years ago. The best hunting grounds are deserts, cliffs and quarries where no soil hides the rocks beneath. Since 1950 dozens of new dinosaurs have come from the dry regions in Argentina, Canada, China, Mongolia, Australia and the United States. Experienced fossil hunters walk slowly, staring at the ground. The clues they are looking for are ancient teeth on its than your thumb and could easily be mistaken for a shiny or layer or rock until frost of rain began to break it up. When floors of gullies excellent grounds. When experts find a fossil, they know more may he lie higher up the slope. Patiently, they must search the rocks above. If embedded in a layer of rock, but finding it is often the easy part. Freeing the bones may be much more difficult.


 * Important Finds
 * Dinosaur - When Named
 * Megalosaurus - 1984
 * Iguanodon - 1925
 * Hadrosaurus - 1958
 * Hypsilophodon - 1869
 * Allosaurus - 1877
 * Apatosaurus - 1977
 * Stegosaurus - 1877
 * Diplodocus - 1878
 * Triceratops - 1889
 * Brachiosaurus - 1903
 * Tyrannosaurus - 1905
 * Ankylosaurus - 1908
 * Protoceratops - 1923
 * Pachycephalosaurus - 1943
 * Deinonychus - 1969
 * Baryonyx - 1986

Collecting Fossils
Digging up a fossil dinosaur is hard work. The bones may be difficult to get to. Rocks can often be as hard as a brick and the bones so soft that they crumble between your fingers. Scientists have to solve the problem of how to free these ancient bones without damaging them.

A Polish scientist carefully chips away soft rock from the backbone of a big flesh-eating dinosaur that once lived in what is now from Gobi Desert.

If the ground is fairly soft, the fossil hunters begin by digging around the bones. This helps them judge the shape and size of the skeleton. Often much of it is missing. If the dinosaur is small and is lying in the soft ground, one or two people may be able to dig it out quite quickly. But a big dinosaur can take a large team weeks of work before it is freed. First, the workers may have to bulldoze, or even blow up, several rock layers to get at the deeply buried bones. Then they use dills or picks and shovels to home in on the fossils. When they reach the bones, they use sharp awls or builder's trowels to chisel away any small, remaining bits of rock. As they find the bones, the hunters photograph and number each one. They also make a chart to show where each bone lies. All this will help the laboratory workers who will piece the skeleton together later on. Removing the bones is another tricky job. A large skeleton is sometimes cut out of the rock in blocks of stone with the bones still inside. Big bones are cushioned with plastic foam or sackcloth soaked in plaster, while small, fragile fossils get a coat of glue or resin to make them strong. The bones need to be well protected; their next move could be a long and bumpy ride before they reach a safe home in a museum.

A bonehead's skull lies embedded in rock before being removed and sent to a museum for carefully study. Fossil remains such as this help scientists work out what the dinosaurs like and how they lived.


 * 1) Digging up dinosaurs can mean spending weeks in hot, dry countryside far from any town.
 * 2) Scientists take photographs of the uncovered bones to show exactly how they were buried.
 * 3) A scientist packs a fragile home in sackcloth and wet plaster. This will form a hard overcoat to protect it.
 * 4) Workers load the heavy plaster-covered bones onto a track ready to be transported to the museum.

Finding Fossils
Anyone can be a fossil hunter. The best hunting grounds are slopes where layered rocks such as shales and limestones show up on the surface. (Remember to keep away from high cliffs where rocks might fall on you.) To collect fossils you will need: a hammer and chisel, a builder's trowel an old notebook where and when you newspaper. At home, use an old you should then write a label for you found it and how old it is. Your local museum or library will b able to help you find this information. Finally, you can store trays made from small boxes or in special drawer.